Why I can't cut there with the knife tool, I want to make a quad out of this n-gons
You can Cut Trough by pressing Z while knifing 


  Allow the Cut tool to cut through to obscured faces, instead of only the visible ones.


or using Knife selection Shift-K (by default) 


  Activates the knife with another set of options so only selected faces are cut and Cut through is on by default.


Knife Tool